Dogs are the oldest domesticated animals. They are also the only animals that have been known to accompany humans in different environments and eras no matter the geographical location of the community. From freezing Siberia to hot deserts of Egypt, there is enough historical evidence to support the view that dogs have evolved at the same time and pace as homo sapiens.

It comes as no surprise that tracing the evolutionary history of dogs is also tracing the evolution of humans from hunter-gatherers to city dwellers. As people changed the way they lived, ate, and functioned as a community, their canine companions evolved, too. However, because scientists have found multiple sites that could be pointed to the regions where dogs were first domesticated, and where they split from wolves, it is not easy to map a specific timeline. Also, new pieces of evidence in the form of old fossils or DNA samples keep shifting the dates, although there is scientific consensus that domestication of dogs began somewhere between 10,000 and 30,000 years ago.

The second stage of evolution of dogs where they were bred for selective traits is said to have been created in the past 200 years, which is a short period in comparison to other evolutionary events in nature. And within this time frame, we have had over 400 dog breeds. Surprisingly, the tiny Chihuahua and the Great Dane are exactly the same species—Canis familiaris—even if they look worlds apart.

Dogs share a unique bond with humans as our closest companions and the first domesticated animals. Stacker shows how through association, mutually beneficial bonding, domestication, and selective breeding, humans have left a permanent imprint on the evolution of dogs.